1. Field of the Invention
The invention relates to a digital telephone communication system, for example ISDN or ISPABX, comprising at least one exchange and at least one user station, the exchange communicating with the user station by way of at least a signalling (D) channel and a voice (B) channel.
2. Description of the Related Art
In digital telephone communication systems such as ISDN (Integrated Services Digital Networks) and ISPABX (Integrated Services Private Automatic Exchanges), the connected user stations are customarily programmed from the exchange. In that case the user need not program the user station himself. A simple example of this relates to a telephone terminal comprising a display device on which the name of the calling person is displayed before the telephone connection itself is established. Together with the ringing signals the exchange thereto sends the telephone number and the name of the calling person to the called person by way of the D channel. The subsequent speech signals are then transmitted over the B channel.
Further types of programming information may also be supplied to the user by the exchange. For example, the exchange may define which user facilities are assigned to each user. The exchange may also remotely program various facilities such as names, numbers, etc. under function keys of the keyboard in the user station. Even remote adjustment of the baud rate, parity and the number of stop bits of a data port in the user station is feasible in this manner. A disadvantage of such a system is that such programming information must correspond to the type of exchange used, because signal transmission by way of the D channel depends on the type of exchange used. In addition, the load on the exchange is increased according as the programming information becomes more extensive.